Synthesis And Properties Of Thieno[2,3-f]Benzofuran-based Organic Photovoltaic Materials

According to the basic concept of the organic polymers,a series of broad absorption and narrow band gap conjugated polymers were designed and synthesized in this paper. Organic solar cells were fabricated using them blended with PCBM as active layers, and the relationship between structure and properties were characterized. The main results are as follows:(1) A two-dimensional thieno[2,3-f]benzofuran monomer as donor unit has been firstly synthesized which is used for a narrow band gap conjugated polymer PTBFTDTBT by Stille coupling polymerization. The synthesized copolymer show good solubility in common organic solvents, such as chloroform, tetrahydrofuran and chlorobenzene with excellent film forming properties. PTBFTDTBT has a relatively deep HOMO level (-5.20eV), and broad absorption and moderately hole mobility (2×10"3cm2· V-1· s-1). Based on the blend of PTBFTDTBT and PC71BM (1:2, w/w),photovoltaic devices without any device optimization show the best photovoltaic performance with a PCEof6.42%, a Voc of0.78V, a Jsc of13.51mA/cm2and a FF of61%,under illumination of AM1.5G (100mW/cm2).(2) With different acceptor units, two new D-A conjugated polymers (PTBFTDTBO and PTBFTDTBTz)containing two-dimensional thieno [2,3-f]benzofuran donor units have been synthesized by Stille coupling polymerization.The two polymers were characterized in detail.Both coplymers show good solubility in common organic solvents, excellent film forming properties, broad absorption (300-700nm). However, here is slightly low performance photovoltaic devices. The devices based on the blend of PTBFTDTBTz:PC71BM (1:1, w/w) exhibited the best device performance with a PCE of3.60%, a Foc of0.61V, a Jsc of10.62mA/cm2and a FF of55.5%under illumination of AM1.5G (100mW/cm2). When3%DIO was added to the blends of polymers and PC71BM, which improved morphology of the active layer, facilitated charge separation and transport, thereby improving the short circuit current to get optimize device performance. (3)Owing to Quinoxaline-based having broad absorption band,a new D-A conjugated polymers containing benzo[1,2-b:4,5-b’]-dithiophene (BDT) donor units and6,7-bis(5-(2-ethylhexyl)thiophen-2-yl)-[1,2,5] thiadiazolo[3,4-g]quinoxaline acceptor unit, polymer PBDTBTQ have been synthesized by Stille coupling polymerization.PBDTBTQ show good solubility in common organic solvents, excellent film forming properties,low optical band gap and having potential significant applicati-on in the future.